I have an audio recording of a lecture from the classroom… How do I remove the background noise or sound/ambience sound
If it’s mono (one blue wave) post about 20 seconds of it here. If it’s stereo (two blue waves) then you only get 10 seconds.
https://forum.audacityteam.org/t/how-to-post-an-audio-sample/29851/1
In general there are only two ways to capture a lecture. Get the performer to wear the microphone or get a tap from the house or classroom sound system. There is no sitting in the audience with a smartphone and getting a clean recording.
If you’re shooting a movie and you buy the classroom, then you can do this.
Or if you’re forced to be in the audience, you can do it this way.
The Noise Reduction tool depends on the background noise being constant and never changing such as microphone hiss, hum or electronic buzz problems. If the noise is always changing like traffic or conversations or music, you’re stuck.
Koz
One more. We can’t take out echoes. If it sounds like a recording from a bathroom, it will always sound like that.
Koz